Billy could see the change in her like a switch was flipped. He hadn't meant to provoke her like that but boy did it really provoke her. If he thought she had been hitting hard before he was wrong, he was so very, very wrong. She hammered him with blows and it was all he could do to keep her from seriously hurting him, focusing all his energy just on defending himself and not even trying to hit back, he couldn't risk leaving himself open and having her bruise or crack a rib.

Plus, this seemed like maybe something she needed. Valkyrie needed to let out some of her anger and rage at her friend being gone and there wasn't anything or anyone she could properly direct it to. So Billy let it direct her to him. Blow after blow just rained down on him and he deflected them the best he could. Eventually thought he had to stop it, for his own sake and because if Valkyrie seriously hurt him she'd feel miserable too.

"I give, I give!" he shouted, hoping that would snap her out of it. "Valkyrie, I give up, stop!"